Conventionally, various work machines such as a demolishing machine in which a work attachment is attached to a base machine have been proposed. For example, a demolishing machine with a super long attachment used in demolishing a high-rise building as disclosed in Patent Document 1 is configured to be able to receive or transport a long work attachment 4 in a folded state.
As illustrated in FIG. 8, this demolishing machine includes a base machine 3 and a work attachment 4 attached to a front part thereof. The base machine 3 includes a crawler-type lower traveling body 1 and an upper turning body 2. The upper turning body 2 is mounted on the lower traveling body 1 so as to be revolvable about a vertical axis.
The work attachment 4 includes a boom 5, a short inter-boom 6, an arm 7, and a work device 8. The boom 5 is attached to the base machine 3, specifically to the upper turning body 2 of the base machine 3, so as to be freely raised and lowered. The inter-boom 6 is attached to a distal end of the boom 5 so as to be rotatable about a horizontal axis in order to expand the working range of the work attachment 4. The arm 7 is attached to a distal end of the inter-boom 6 so as to be rotatable about the horizontal axis. The work device 8 is attached to a distal end of the arm 7. The work device 8 illustrated in FIG. 8 is a crushing device called a nibbler.
The boom 5 includes a main boom 5a and a front boom 5b that is detachably connected to an upper end side thereof. When the demolishing machine is transported, the demolishing machine is disassembled into the base machine 3 and the work attachment 4. In this case, the main boom 5a is transported in a state of being attached to the base machine 3.
Although the front boom 5b is generally formed by detachably connecting a plurality of stages of booms, a single-stage front boom is illustrated for the sake of simplicity.
Moreover, a boom cylinder 9 that raises and lowers the boom 5 and the entire attachment including the boom 5, an inter-boom cylinder 10 that operates the inter-boom 6, an arm cylinder 11 that operates the arm 7, and a work device cylinder 12 that operates the work device 8 are provided as a cylinder such as a hydraulic cylinder that operates the work attachment 4.
The inter-boom cylinder 10 is provided between the boom 5 (specifically, the front boom 5b of the boom 5) and the inter-boom 6, and the arm cylinder 11 is provided between the inter-boom 6 and the arm 7, respectively, on the belly side (that is, the side facing the front side (the direction indicated by arrow F) of the base machine 3) of the attachment.
The work device cylinder 12 is attached to a distal end side of the arm 7 on the back side (that is, the side facing the backward side (the direction indicated by arrow R) of the base machine 3) of the work attachment 4 in a state where the work attachment 4 is extended to stand up.
When such a demolishing machine with a super long attachment is disassembled, as illustrated in FIG. 8 (see the solid-line portion) and FIG. 9, the work attachment 4 is placed on a ground in a three-fold state so that the boom 5 is disposed above the inter-boom 6 and the arm 7 is disposed below the inter-boom 6. In this state, as described above, the demolishing machine is transported in a state of being separated into a group composed of the base machine 3 and the main boom 5a and a group composed of the work attachment 4 excluding the main boom 5a. The group of the work attachment 4 is transported in a posture where the entire group is folded.
However, in a state where the work attachment 4 is in the folded posture, since the work device cylinder 12 is positioned below the arm 7, when the attachment 4 is placed directly on a ground or the like in a folded state, the work device cylinder 12 may be damaged. Thus, conventionally, a bracket 13 that protrudes toward the lower side of the arm 7 is provided. By allowing the bracket 13 to make contact with a ground, the work attachment 4 can be placed on a ground or the like in a state where the arm 7 is above a ground or the like. However, in the configuration where the bracket 13 is provided, there is a problem in that the height H1 of the attachment 4 increases when the attachment 4 is placed on a ground or the like in a folded state.
Moreover, in order to decrease the height H1, a structure may be taken into consideration in which in a state where the attachment 4 is in a folded posture, the work device cylinder 12 is attached to a surface facing upward of the arm 7, a surface facing downward of the arm 7 is flat, and the flat surface is placed directly on a ground. However, in this case, since the position of the work device cylinder 12 in relation to the arm 7 is greatly different from that of a conventional work machine, a method of operating the demolishing machine is changed greatly, which may influence the operability during demolishing.
There is another problem in that, when the work device cylinder 12 is attached to a surface facing upward of the arm 7, in a state where the attachment 4 is in a folded posture, the disposition of the arm 7 and the boom 5b in a close proximity with each other becomes difficult to implement.
Moreover, in order to secure the space for receiving the work device cylinder 12 between the arm 7 and the boom 5b in the folded posture of the attachment 4, it is necessary to attach the boom 5b in a state of being inclined upward with respect to the extension direction of the arm 7. The height of the attachment in the folded state increases. Further, since the entire height of the boom 5b is not constant, it is not desirable from the perspective of transporting property and maintenance operability.    Patent Document 1: Japanese Patent Application Publication No. 2007-203221